fix(types): allow css: false option

[lukeed]

readme declares css: false but types disallowed it

[benmccann]

This looks fine to me. Or alternatively we could update the readme? It'd save us from having to cut a new release. I think that not providing css (i.e. css: undefined) is equivalent to css: false

[lukeed]

This needs to be here either way -- otherwise IDE yells about invalid option(s)
The official template also uses css: boolean and is "an error" by default.

Also, versions are cheap -- especially patches.

[lukeed]

Thanks~!